virtio-console: avoid DMA from stack
put_chars() stuffs the buffer it gets into an sg, but that buffer may be on the stack. This breaks with CONFIG_VMAP_STACK=y (for me, it manifested as printks getting turned into NUL bytes). Signed-off-by: Omar Sandoval <osandov@fb.com> Signed-off-by: Michael S. Tsirkin <mst@redhat.com> Reviewed-by: Amit Shah <amit.shah@redhat.com>
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@ -1136,6 +1136,8 @@ static int put_chars(u32 vtermno, const char *buf, int count)
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{
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struct port *port;
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struct scatterlist sg[1];
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void *data;
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int ret;
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if (unlikely(early_put_chars))
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return early_put_chars(vtermno, buf, count);
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@ -1144,8 +1146,14 @@ static int put_chars(u32 vtermno, const char *buf, int count)
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if (!port)
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return -EPIPE;
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sg_init_one(sg, buf, count);
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return __send_to_port(port, sg, 1, count, (void *)buf, false);
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data = kmemdup(buf, count, GFP_ATOMIC);
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if (!data)
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return -ENOMEM;
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sg_init_one(sg, data, count);
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ret = __send_to_port(port, sg, 1, count, data, false);
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kfree(data);
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return ret;
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}
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/*
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